Producer Sue Vertue was at a funeral when someone's cellphone went off. It was, most inappropriately, playing 'Staying Alive'. When her husband, Steven Moffat, heard this he decided it was the perfect ringtone for Moriarty.
Benedict's favorite scene is the ultra-slow motion scene where he opens Irene's safe and they take down the evil CIA agents. "I'll be proud to show that to my grandchildren."
Benedict Cumberbatch fell while dressed only in his sheet at Buckingham Palace. "I'd overstepped my sheet's limits and fell. I was dedicated to the moment." Though it made a terrible sound, cast and crew could not help laughing.
Watson tells Sherlock and Irene his middle name is Hamish. Watson is called John H. Watson in the stories except for a couple of times when he is called James. This puzzled scholars for years until Dorothy L. Sayers suggested the H stood for Hamish, the Scottish version of James.
Re Irene's orgasmic text alert: Moffat said "Texting just isn't sexy, so I had to add something." The first sound they used sounded 'like someone had just been gut-punched." So they got Lara on the phone and made her do lots of longer sexier sounds.